Bluetooth-Only External Radio Coexistence

The Bluetooth® coexistence feature can use the 1-wire LTE coexistence protocol.

Application Programming Interface:

You can find the details of the API in the nrfxlib/mpsl/include/mpsl_coex.h file.

Note

This implementation is only supported on nRF52 devices.

1-Wire coexistence protocol

Interface

The 1-wire protocol lets Bluetooth LE nRF chips coexist alongside an LTE device on a separate chip. It was specifically designed for the coex interface of nRF9160.

Hardware resources

The 1-wire Coexistence protocol requires the following peripherals:

1-wire coexistence protocol HW resources

Peripheral	Count	Description
GPIO pins	1	Pin selected for the 1-wire interface BLE_GRANT
GPIOTE channels	1	One GPIOTE channel for registering BLE_GRANT pin changes
PPI channels	1	Connecting the BLE_GRANT to Radio DISABLE task

Interface signals

The 1-wire interface is a single unidirectional input controlled by the LTE device:

1-wire LTE coexistence protocol pin

Pin	Direction	Description
BLE_GRANT	In	Used by the LTE to grant radio access

The interface consists of a BLE_GRANT signal mapped to the GPIO pin by the application’s interface configuration. The signal’s active level (high or low) is programmable. Whenever the nRF SoC requires the use of the radio for any RF activity, it needs to test that the BLE_GRANT pin level is valid for Bluetooth LE radio use (such as 0 for the nRF9160).

The figure below illustrates these timings with regard to the LTE and BLE_GRANT signal.

1-wire LTE Coexistence protocol timing

When the BLE_GRANT is revoked (for example the pin de-asserts for the nRF9160), the Bluetooth LE radio immediately gets disabled with a maximum delay of 7us.

When the coexistence interface is disabled, the associated GPIO pins are set to a high impedance state.